PGTS Humble Blog

#include <ctype.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

/*
 * The original script was written with Chat GPT 4.0
 *
 * Code was put into a subroutine, so that if any arguments are specified,
 * the processs will attempt to open the arguments as files.
 *
 * Output is written to stdout
 *
 * Gerry Patterson (2025)
 */

#define MAX_BUF 8192
FILE *INP;
unsigned char buf[MAX_BUF];
int ptr = 0;
int use_stdin = 0;
int opt_p = 0;

/* ------------------------------------------------------------------------ */

/* rtrim() - get rid of trailing white space */

char *rtrim(char *ptr)
{
	int i = strlen(ptr);
	for(i--; i >= 0; i--) {
		if(isspace(ptr[i]))
			ptr[i] = '\x00';
		else
			break;
	}
	return (ptr);
}

/* ------------------------------------------------------------------------ */

void store_char ( unsigned char c)
{
	buf[ptr++] = c;
	if (c == 0x0A) {
		if (opt_p) {
			printf("%s\n", buf);
		} else {
			printf("%s\n", rtrim(buf));
		}
		memset(buf, 0, sizeof(buf));
		ptr = 0;
	}
}

/* ------------------------------------------------------------------------ */

void usage()
{
	printf("\n");
	printf("USAGE:\n");
	printf("\tu2asc [OPTION] [FILE]\n\n");
	printf("OPTIONS:\n");
	printf("\t-h [Or any other char] Show this screen.\n");
	printf("\t-p Preserve trailing whitespace on input lines\n\n");
	printf("If no file[s] specified read stdin.\n\n");
	exit(1);
}

/* ------------------------------------------------------------------------ */

int u2asc ()
{
	unsigned int byte1, byte2;
	uint16_t utf16_char;
	char ascii_char;
	int w_read = 0;

	while ((byte1 = fgetc(INP)) != EOF) {
		byte2 = fgetc(INP);
		if (w_read < 2)
			w_read++;
		if (byte2 == EOF) {
			// Handle unexpected EOF (odd number of bytes)
			fprintf(stderr, "Unexpected end of input.\n");
			return 1;
		}

		// Construct UTF-16LE character
		utf16_char = (uint16_t)((byte2 << 8) | byte1);

		// Convert to ASCII
		if (utf16_char <= 0x7F) {
			ascii_char = (char)utf16_char;
		} else {
			// Check for UTF-16 Header word
			if (w_read == 1 && utf16_char == 0xFEFF)
				continue;
			ascii_char = '?';  // Replace non-ASCII with '?'
		}

		// fputc(ascii_char, stdout);
		store_char(ascii_char);
	}
	return 0;
}

/* ------------------------------------------------------------------------ */

/*
 * Process options.
 * See getopt.c for more details
 */

int process_opt(argc,argv)
int argc;
char **argv;
{
	int index;
	int c;
	int argn = 0;

	while ((c = getopt (argc, argv, "ph")) != -1) switch (c) {

		case 'p':
			opt_p++;
			break;

		case 'h':
			usage();

		case '?':
			/* sanity check options */
			printf("\nERROR Unrecognised option, Valid options are as below:\n");
			usage();
		default:
			break;

	}
	if (optind == argc) {
		/* no file specified - use stdin */
		INP = stdin;
		return (1);
	}
	return(0);
}

/* ------------------------------------------------------------------------ */

int main (int argc, char **argv)
{
	int i;
	use_stdin = process_opt(argc, argv);
	if (use_stdin) {
		// Read data from stdin
		u2asc();
	} else {
		for (i = 1; i < argc; i++) {
			if ( (INP = fopen( argv[i], "r" ) ) == NULL ) {
				fprintf(stderr,"ERROR Cannot open file: %s\n",argv[i]);
				// Could replace this with continue?
				return(1);
			}
			if (u2asc()) {
				printf("\n");
				fprintf(stderr,"ERROR Processing file: %s\n",argv[i]);
				return(1);
			};
			fclose(INP);
		}
	}
	return(0);
}